Got some new Lead Acid 12v batteries. When charged one 12v is showing 10.5v and the other one 13v (The charger thinks they are full). These batteries are for a cordless lawn mower, and I am using a 24v charger. Not sure how I can get rid of the unbalance. Any ideas?

Hirobo XSpec EVOHirobo SDXFutaba 12Z FASST

Disconnect them and connect them in parallel. By that I mean take them out of the mower and attach the positive leads together and then the negative leads together. Leave them that way for a day or two and then put them back in and try charging them again.

Uh huh.....

Team Futaba Team Kontronik USA

An update:

Sorry, it is non helicopter related

Well, the people at the service place don't really know much about this mower I have, they said the battery was fine, but once I put a load on it, the V dropped like a stone. They did not believe me and refused to change it...

I have been playing around with it a little bit, I ran the lawn mower around today, hardly any power, for a while. I then recharged the battery that seems bad, with a separate charger. I then popped it back in and now it is getting better. It only drops down to 10.3V instead on the 7V before. So, maybe I am on to something here. I will run the mower tomorrow again and then charge it up and see what happens.

The strange thing was that the battery was warm on one side I short side) of the battery, but not the other one, after I ran the mower for a while...

Hirobo XSpec EVOHirobo SDXFutaba 12Z FASST

Henrik Engert

One of your batteries has a bad cell. There is nothing that you can do about it. It will have to be changed. Hooking them together in parallel will not do anything as there is no way for one cell to be low without it being bad. All batteries are a collection of cells in series(and parallel if needed) and they must charge properly while still connected in series. Each section of the cells that is permanently connected together ie. the individual 12v batteries must display 12.65 volts after charge at rest after surface charge removed or there is a bad cell in that section. If they are new then it is a warranty issue. If the people who sold you the unit won't replace it then sue them for new ones and also for being ignorant/stupid as what I have told you is common lead/acid battery fact.

After rest the battery shows 12.35V

Hirobo XSpec EVOHirobo SDXFutaba 12Z FASST

Henrik Engert

Still not charged. It should never have been at 10 volts at rest UNLESS it had either a bad cell or been over discharged down to that voltage across all the cells. Either way it is not good for the battery and even if you did get it up to 12 volts it's life is shortened.